Radio receiving circuit



Jan. 28, 1930. M. voN ARDENNE RADIO RECEIVING CIRCUIT Filed NOV. 11, 1926 AAAA INVENToR MnNFReomHM/vmf Patented Jan. 28, 1930 UNITED sTATEs PATENT OFFICE MANFRED VON ARDENNE, OF BERLIN, GERMANY, ASSIGNORTO RADIO `CORIOIR'A'IIC'IN' 0 AMERICA, A CORPORATION OF'DELAWARE RADIO RECEIVING CIRCUIT Application filed November 11, 1926, Serial No. 147,656, and in Germanyv October 2.1, 1925.

An application for patent for this invention has been filed in Germany, on October 21,1925.

This invention relates to a receiving arrangement and more particularly to an arrangement wherein a resistance coupled amplifier is used for both radio and audio frequency amplification.

Although, as has been found by research of the applicant, the most favorable conditions for attaining effective amplifications with the use of the so-called potential amplifier principle are not the same for radiofrequency and audio-frequency currents, it has also been discovered that resistance-coupled ra- Y dio frequency/'amplifiers allow of an ampliiication, as hereinafter described, which results in a substantial improvement in the conditions of reception, and their use insures a saving in the first cost of efficienti receiving apparatus.

The so-called reflex principle in connection with the ordinary type of amplifier tube is well known. That is, the tube canbe employed for the simultaneous amplification and rectification of radio frequency currentsv rand for the reflection and renewed amplification of the resultant low frequency impulses. However, while radio frequency amplifiers are usuallyworlred with tuned radior frequency circuits or choke coils, it has of late been possible to build radio frequency amplifiers with purely ohmic resistancesjallowing of an eicient radio frequency potential amplification down to very short waves. Although such resistance-coupled .radio frequency amplifier tubes fail to give atthe same time most favorable conditions for the'amplification of low-frequency currents, it is nevertheless true that their amplifying power is sufcient for all practical purposes.

It is an obj ect of this invention to use such f a resistance-coupled potential amplifier tube, in conformity with the reflex principle, for the amplification of the ensuing low frequen cy impulses, without incidentally impairing its radio frequency amplifying powers. With a single multi-stage resistance-coupled radio frequency amplifier it is thus feasible to attain particularly good receiving action. As

it were, the whole resistance-coupled radio y frequency amplifier can be treated as a single reecivertube, and, according to the reflex principle, the incoming energy, changed into low frequency energyeither by the amplifier itself or by a separate detector, is again passed through the resistance coupled radio.

for instance, to raise signals, which after simple radio frequency amplication and rectification are just audible, by renewed low frequency amplification in the same amplifier to a strength adequate for loud speaker operation.

Another object of this invention is'to yprioi vide areceiving arrangement wherein only a single audio transformer is necessary for reflexing in a 'multi-stage` amplifier. Y

Heretoforek it was necessary that such ya transformer be used with each amplification stage, but with the circuit herein disclosed, the need for a plurality yof audio frequency transformers hasvbeen dispensed with.' The operation of the receivingarrangement accordingto thisinvention is diagrammatically illustrated in the drawing.

The radio.- frequency energy picked anfopen antenna or by a loop or coilantenna l, preferably afterfhaving been tuned, Visfed by meansl of a 'coupling l through circuit 2 tothe grid 3 of the first. stage ofthe resistance-coupled radio frequency potential am- Numerals 4, 5, 6 designate the filaments of three tubes numbered 4', 5', and 6 respectively` which are heated from the battery 7.. 8 is the plate battery; 9 andlO are high-ohmic plateresistances; 11,'and 12, aregrid leaks;

while-13 andli' are coupler condensers. In the output circuit of thethird amplifier stage there is inserted an anti-resonant circuit l5v tuned to radio frequency. The coil l5 of circuit 15 is coupled to a coil 16', and the output from the latter is rectified, for instance,

y a crystal or tube detector 16.

But the signal heard in the telephone receiver 17 is small. However, if an audio frequency transformer 18 is inserted in the detector circuit 16, and if the low frequency energy is again fed to the grid circuit of tube 4 through the leads 20, 21, then the lo1 fre- 10 quency energy will be eiciently amplified by the resistance coupled potential amplifier.

The amplified audio frequency currents are utilized in any Well known manner, as by a loud speaker 19 inserted in the plate circuit l5 of the tube 6.

In the use of the reflex principle as hereinbefore described, the telephone receiver 17 inthe detector circuit may, of course, be dispensed with since the loud-speaker in the ,s ptite circuit of the third tube takes the place of the telephone.

What may be emphasized as a. special feature of the present invention when contrasted with the well known reflex circuit arrangegg ments is that by the method disclosed in this invention it is possible for the first time to utilize all of the tubes for low frequency reflex effects. In the reflex connections heretofore disclosed, this has not been possible for so the reason that ordinarily at least one tube of the arrangement was arranged so as to be suited only for radio frequency amplification, in other words, only one coil of a few turns for example, was inserted in the plate al circuit, or a. tuned oscillation circuit. Hence, the low frequency reflex actionl according to the present invention allows a more efficient utilination of the existing tube equipment than has been true of refiex circuit arrangem ments heretofore used.

I claim asmy invention:

1. vIn a receiving circuit, a multi-stage resistance coupled radio frequency amplifier, means including a tuned circuit for control- 4e. ling the input to said amplifier, a system tuned to radio frequency in the output circuit of the end stage of said amplifier, and means coupled to the tuned system including a single audio frequency transformer and a n crystal detector for reflexing the audio output of the end stage of saidresistance coupled amplifier through said resistance coupled amplifier.

i. In a radio signalling system an antenna,

w a multi-stage resistance coupled amplifier, means for coupling said amplifier to saidA antenna, a tuned circuit in the output circuit of the end stage of said amplifier, and means coupled to the tuned circuit and including a 00 contact rectifier for refiexing the audio frequency output of the end stage of said amplifier into the first stage of said amplifier.

MANFRED voN ARDENNE. 

